Postoperative Ileus with the Topical Application of Tongfu Decoction Based on Network Pharmacology and Experimental Validation

Objective Postoperative gastrointestinal dysfunction is a common and important complication of surgery. This study aimed to explore the key pharmacological mechanisms of Tongfu decoction in treating postoperative ileus (POI). Methods The active ingredients of Tongfu decoction and their targets were screened using the TCMSP database and STITCH and SwissTargetPrediction databases, respectively. The GeneCards and DisGeNET databases were used to obtain POI dysfunction-related therapeutic targets. After screening, a drug-active-ingredient-therapeutic target network was constructed and the key target functional enrichment analysis was carried out. The Sprague–Dawley rats with POI were used for in vivo experimental verification. The serum levels of IL-1β, IL-6, IL-10, IFN-γ, and MCP-1 were measured after surgery using enzyme-linked immunosorbent assay. The Western blot analysis was used to determine the expression of key proteins of the PI3K-Akt signaling pathway in colon tissues. Results An interaction network was constructed containing 7 Chinese medicine components, 36 compounds, and 85 target proteins. The functional enrichment analysis showed that the target proteins mainly acted on the POI through the PI3K-Akt signaling pathway. In in vivo experiments, Tongfu decoction had a promoting effect on the serum level of IL-10, an inhibitory effect on the serum levels of IL-1β and CCL2, and an inhibitory effect on the local expression of PI3K, pAkt, and mTOR in colon tissue. In addition, the Tongfu decoction increased the intestinal ink advancing rate. Conclusion Nonoral Tongfu decoction can also be used to treat POI; its mechanism is affected by IL-10 and IL-1β.The inhibition of the PI3K-Akt signaling pathway affected the treatment with Tongfu decoction by inducing an immune-inflammatory storm in POI.


Introduction
In this study, the key pharmacological mechanism of Tong fu decoction, a traditional Chinese medicine (TCM), in treating postoperative gastrointestinal dysfunction was mainly explored through network pharmacology and experimental verification. Postoperative ileus (POI) is one of the major postoperative complications of gastrointestinal surgery. Its etiology has been mainly classified into two stages. e early stage is 3-6 h after surgery, during which sympathetic inhibition is induced by surgical stimulation. e second stage is 6-72 h after surgery, during which an immune mediatordriven inflammation occurs [1]. If the patient is unable to recover within 120 h, these complications may lead to more serious consequences [2] and even death.
At present, the main way to prevent and treat POI is the promotion of enhanced recovery surgery (ERAS). ERAS was proposed by Kehlet in the 1990s, and it has been continuously optimized and improved. ERAS is a multidisciplinary, individualized diagnosis and treatment discipline involving a team of surgeons, anesthesiologists, and nursing staff. Its main purpose is to speed up the postoperative rehabilitation process and reduce the incidence of postoperative complications [3]. e content of ERAS in modern medicine includes fasting for 2 h before surgery, application of minimally invasive surgery, improvement in anesthesia plan, liquid management of postoperative parenteral nutrition, reasonable drainage tube removal, and preoperative and postoperative missions [4].
e main purpose of this treatment is to shorten the length of hospitalization and reduce the cost of hospitalization and incidence of postoperative complications, but the problem of poor compliance still exists.
In previous studies, TCM promoted the recovery of patients [5][6][7][8][9][10][11] and had a synergistic effect on ERAS [12][13][14][15]. One of the drugs used was Tongfu decoction, having a certain effect on POI using nonoral treatment methods such as rectal instillation, which could accelerate the recovery of postoperative gastrointestinal function and relieve postoperative inflammation of the digestive tract [16][17][18][19]. e theory of TCM believes that the treatment of Tongli Gongxia, which lowers the adversity and regulates qi, can relieve abdominal distension, nausea, and vomiting in patients with POI. Also, it promotes postoperative defecation and inhibits inflammation [20]. Despite some promising clinical evidence, the pharmacological mechanism of Tongfu decoction in treating POI remains unexplored.

Screening of Active Compounds in Compound
Prescriptions.
e TCMSP database, which is a pharmacological database and analysis platform of the Chinese medicine system (http://lsp.nwu.edu.cn/tcmsp.php), was used in this study. e database included 499 Chinese medicines registered in the Chinese Pharmacopoeia, containing 29,384 ingredients, 3311 targets, and 837 related diseases. e disease information in this database comes from the TTD and PharmGKB databases. e active ingredients of Rhubarb, Magnolia officinalis, Fructus Aurantii, Angelica sinensis, Toosendan Fructus, and Aucklandiae Radix were searched in the TCMSP database using OB and DL as indicators, ADME as a comprehensive model, and oral bioavailability of OB ≥ 30% and drug similarity DL ≥ 0.18 as screening thresholds.

Screening of Active Compound
Targets. STITCH (https://stitch.embl.de/) and SwissTargetPrediction databases were used to screen the targets of active compounds of Tongfu decoction obtained in Section 2.1.1. e PubChem database (https://pubchem.ncbi.nlm.nih.gov/) was used to add all the active compounds to the STITCH database. e compound was converted into the standard canonical SMILES format and imported into SwissTargetPrediction. e target with parameter probability >0 was selected for further analysis.

Construction of Pharmacologically Active Compound-Target Protein
Network. Based on the results of the target proteins of the pharmacologically active compounds screened using STITCH and SwissTargetPrediction, Cytoscape was used to construct the "pharmacologically active compound-target protein network" in the compound.

Screening for Targets of POI.
GeneCards (https://www. drugBank.ca/) and DisGeNET (https://www.disgenet.org/) were used to uncover the genes that affected POI. e intersection targets of genes that affected POI and the target protein of the compound with drug activity were the key research objects.

Constructing Key Target PPI Networks.
A key target PPI network was constructed using the STRING (https:// stringdb.org) website to understand the functions and connections of the aforementioned proteins. Cytoscape completed the drawing and beautification of the network.

GO and KEGG Enrichment
Analyses. GO enrichment and KEGG analyses on the intersection genes were conducted in the R software clusterProfiler package. Pathview was used to visualize the KEGG pathway. GO enrichment analysis mainly described the biological processes (BP), cellular components (CC), and molecular functions (MF) correlated with genes.

Composition of Tongfu Decoction.
e external preparation of Tongfu decoction comprised Chinese medicine decoction pieces. ese pieces were selected by Beijing Tongrentang Pharmaceuticals. e specific ingredients were as follows: Rhubarb, M. officinalis, Fructus Aurantii, A. sinensis, radish seeds, Toosendan Fructus, and Aucklandiae Radix. e aforementioned drug was crushed and mixed with petroleum jelly. e weight ratio of drug:petroleum jelly was 1 : 2 to make a plaster with a weight of 5 g.

Animal Experiments.
e experimental animals were healthy male Sprague-Dawley rats, aged 9-10 weeks, and weighing 200 ± 10 g, which were routinely reared. ese rats were divided into model (small intestine surgery) group, negative control (abdominal incisions only) group, Tongfu decoction group, neostigmine group, and blank group. Each group was randomly divided into postoperative 24-h, 72-h, and 120-h groups. e rats in each group were fasted for 24 h before surgery and allowed to drink water ad libitum. e method of modeling was an aseptic operation, which involved opening the abdominal cavity via a midline incision of the abdomen, turning the small intestine to the left, placing it on the gauze soaked with normal saline, and squeezing from the dactyly to the ileocecal area. is step was to simulate the clinically common whole small-bowel explorative surgery. e rats in the negative control group only underwent opening of the abdomen and intestines without pushing operation. en, the small intestine was returned in order, a small amount of saline was sprinkled 2 Evidence-Based Complementary and Alternative Medicine into the abdominal cavity, and the abdominal cavity was closed with intermittent sutures. After the surgery, the rats were subcutaneously injected with 20,000 IU/kg penicillin G sodium and 250 mg/kg streptomycin sulfate on the back for three consecutive days. In the neostigmine group, 10 µg of neostigmine mesylate was subcutaneously injected daily.
e Tongfu decoction was applied to the scapular skin of the rats in the form of a patch and fixed with tape. e dressing was changed every 24 h. After the surgery, the rats were fasted for 48 h without water and given 20% glucose solution twice in the morning and evening at an interval of 8 h. On the third day after the surgery, 20 mL/kg feed paste was fed (standard feed was superfinely pulverized, and 20% feed paste was prepared).
e diet was provided free on the fourth day.

Enzyme-Linked Immunosorbent Assay, Western Blot, and Hematoxylin and Eosin
Staining. e serum levels of IL-1β, IL-6, IL-10, IFN-c, and MCP-1 (Proteintech, China) in rats were detected by enzyme-linked immunosorbent assay (ELISA) after 1 day, 3 days, and 5 days of the surgery. A BCA protein determination kit (BioSharp, China) was used to determine the total protein content of rat colon tissue 24 h after the surgery. An equal amount of protein was separated using a 10% SDS-PAGE gel and transferred to a polyvinylidene fluoride membrane (Millipore, USA). After blocking, the membrane was incubated with the corresponding primary antibodies (PI3K, Akt, pAkt, and mTOR) at 4°C overnight. After washing with TBST, the membrane was incubated with the secondary antibody for 1.5 h. e villus ratio of all antibodies was 1 : 5000 (Proteintech, USA). Western blot detection used ECL chemiluminescence detection (BioSharp, China) and Amersham imager600 (Tianneng, China). e colon tissue of the rat was taken 24 h after the surgery, fixed with 10% formalin, embedded and cut into 4-μm sections, and stained with hematoxylin and eosin (HE); the tissue morphology was observed.

Statistical Analysis.
e data between groups were analyzed using one-way analysis of variance (SPSS 28.0). e Student t-test was used for the data between the two groups. ese results were presented as the mean ± standard error of the mean for the treated experimental and control groups.

Active Ingredients and Targets in Tongfu Decoction.
e active ingredients corresponding to Rhubarb, M. officinalis, Fructus Aurantii, A. sinensis, Toosendan Fructus, and Aucklandiae Radix were uncovered by searching in the TCMSP database (Table 1)

Potential Target of Tongfu Decoction in Treating POI.
Based on the results of the target proteins of the pharmacologically active compounds screened by STITCH and SwissTargetPrediction, Cytoscape was used to construct a compound with pharmacological activity-target protein network, which contained 39 compounds and corresponding 649 target proteins (Figure 1(a)).
en, the genes that affected POI were screened using GeneCards and DisGeNET, and the intersection with the target protein of the drug-active compound in Figure 1 was taken, obtaining 85 overlapping genes (Figure 2(a))

PPI Network Establishment.
A PPI network based on 85 intersection genes was created using the STRING website ( Figure 2(b)). Cytoscape was used to complete network drawing and beautification (Figure 2(c)). A drug-active ingredient-target protein network was further established (Figure 2(c)).

GO and KEGG Enrichment
Analysis. GO enrichment analysis was performed on 85 intersection genes, and the most significantly enriched 10 GO terms in BP, CC, and MF categories were revealed, as shown in Figure 3(a). e top 5 GO BP terms were "response to drug," "response to lipopolysaccharide," "response to molecule of bacterial origin," "response to oxidative stress," and "cellular response to chemical stress." KEGG enrichment analysis was also performed on the intersection genes, and the 30 most significant signaling pathways were identified, as listed in Figure 3 e parts closely related to inflammation were screened. Among these, the PI3K-Akt signaling pathway was significant for POI (Figures 3(b) and 3(c)).

Effect of Tongfu Decoction on the Intestinal Function of Rats with POI.
e pass rate of the intestine for rats with POI was measured to verify the therapeutic effect of Tongfu decoction on POI. e intestine passage rate was significantly higher in rats using Tongfu decoction than in those in the model and neostigmine groups on the third day after the surgery (p < 0.01), suggesting that Tongfu decoction had a certain effect on POI treatment (Figures 4(a) and 4(b)). e rat colon tissue was HE stained. Rats using Tongfu decoction had a much more complete colonic mucosal epithelial structure and less infiltration of eosinophils, neutrophils, and lymphocytes in colon villi and muscle tissues. Also, they were less prone to vasodilation ( Figure 4). ese results showed that Tongfu decoction improved the inflammatory pathological changes that occurred after the surgery of the colon tissue in rats. e rats using Tongfu decoction exhibited a significant increase in the serum level of IL-10 on the first day after the surgery (p < 0.01) and a significant decrease in the serum levels of CCL2 and IL-1β on the fifth day (p < 0.01) ( Figure 5). e expression levels of PI3K, pAkt, and mTOR in the colon tissue of rats treated with Tongfu decoction reduced compared with those in the model group (p < 0.05) ( Figure 6).

Discussion
e main components of Tongfu decoction are tannins, anthracene derivatives, stilbene derivatives, phenbutanone, and naphthalene derivatives. ese components increase intestinal mucosal motility, inhibit intestinal water absorption, exert anti-inflammatory effects, and reduce cytokine secretion [21][22][23]. Glauber's salt is a natural mineral with Na 2 SO 4 ·10H 2 O as the main component, which has anti-inflammatory and cathartic effects. e pharmacological effects of other drugs such as M. officinalis and Citrus aurantium are related to the improvement in intestinal motility.
is study was conducted to investigate the molecular mechanism of Tongfu decoction in treating POI. Based on the predicted targets of network pharmacology, this study focused on the effects of Tongfu decoction on different immune mediators and the PI3K-Akt signaling pathway. Rats with POI were used as experimental materials to explore the antagonistic effect of Tongfu decoction on the inflammatory response of postoperative colon tissue in rats and to verify the prediction results of network pharmacology. In this study, the network pharmacology methods were used to systematically analyze the TCM compounds in Tongfu decoction at the molecular level. A total of 39 potentially active Chinese medicine compounds, 649 target proteins related to postoperative gastrointestinal dysfunction, 85 potential genes, and 30 most relevant signaling pathways were obtained. According to the KEGG analysis, the signaling pathway with the highest correlation was the PI3K-Akt signaling pathway, suggesting that Tongfu       Evidence-Based Complementary and Alternative Medicine decoction might play a role in treating POI by regulating the PI3K-Akt signaling pathway. is pathway was of great significance in the inflammatory response. is conclusion was confirmed in various experiments. In vivo experiments showed that external application of the Tongfu decoction patch after the surgery could increase the passage rate of small intestinal contents in rats.
is meant that not only oral administration but also a topical patch of Tongfu decoction could promote the recovery of small intestinal function. Western blot analysis and ELISA revealed that Tongfu decoction treated the disease by affecting the mechanism of the PI3K-Akt signaling pathway. Tongfu decoction also reduced the serum levels of CCL2 and IL-1β, increased the serum level of IL-10 and reduced the infiltration of local eosinophils and monocytes in colon tissue.
Previous studies demonstrated a reduction in the levels of CCL2 and IL-1β and an increase in the level of IL-10 had positive effects on the treatment of POI. CCL2 is one of the key chemokines regulating monocyte/macrophage migration and infiltration. Its reduction can improve inflammation and POI [24]. As an inflammatory mediator, IL-1β directly affects the symptoms of POI (gas, defecation, nausea, vomiting, and so on). Its release depends on the number of AIM2 inflammasomes and microorganisms [25]. IL-10 is a potent anti-inflammatory mediator that reduces neutrophil infiltration, cytotoxicity [26], and inflammatory responses induced by intraoperative hemorrhage [27], regardless of sepsis-induced gastrointestinal function [28] or postoperative gastrointestinal dysfunction [29]. e serum levels of IL-10 peaked about 4 h after laparotomy and returned to normal levels within 3 days after the surgery [30]. In this study, the expression of IL-10 increased on the first day after the surgery, while the levels of CCL2 and IL-1β decreased on the third and fifth days after the surgery, suggesting that Tongfu decoction affected the early postoperative inflammatory response. e secretion of anti-inflammatory mediators had an inhibitory effect on the secretion of inflammatory mediators in the long-term intestinal tract. e PI3K-Akt signaling pathway plays an important role in the inflammatory response. PI3K signaling promotes the inflammatory activity of T cells by phosphorylating the FOXO transcription factor [31]. In POI, an excessive inflammatory response is not required, and Tongfu decoction can reduce the activity of the PI3K-Akt signaling pathway. In BV2, LPS treatment did not affect the relative levels of PI3K and NF-κB p65 expression but significantly increased the relative levels of phosphorylated Akt and NF-κB p65, implying that pAkt overexpression might affect not only downstream inflammatory expression but also the nervous system, thereby inducing postoperative gastrointestinal dysfunction [33]. e factors such as CCL2 and IL-1β were in the PI3K-Akt-related downstream signaling pathway, which was consistent with the hypothesis that the regulation of PI3K-Akt signaling pathway could affect the development of inflammation in postoperative gastrointestinal dysfunction. erefore, it was presumed that the main target of Tongfu decoction was the PI3K-Akt signaling pathway. e comprehensive and systematic analysis of drugsactive-ingredients-target proteins in network pharmacology conforms to the holistic concept, and its research concept coincides with the overall concept of TCM syndrome differentiation and treatment. Network pharmacology is often used in the study of TCM components and targets [32][33][34][35][36][37]  Evidence-Based Complementary and Alternative Medicine combination of TCM and network pharmacology bridges the gap between modern medicine and traditional medicine [38]. is study explored the mechanism of Tongfu decoction in treating postoperative gastrointestinal dysfunction and identified a new form of percutaneous topical administration. In previous studies, rectal instillation and jejunal injection were usually chosen for administration [39], which were associated with problems such as poor compliance and further irritation of the digestive tract. e form of administration described in the present study provided greater compliance and was simpler than rectal instillation [39,40]. Moreover, transdermal administration did not consider liver toxicity; only local allergic reactions were considered, and it was highly safe. In   Figure 5: Effects of Tongfu decoction on the expression of IL-6, CCL2, and IFN in villi and muscle tissues and IL-10 (days 1, 3, and 5) after surgery (compared with the model group, * * * * p < 0.0001, * * * p < 0.001, * * p < 0.01, and * p < 0.05).
addition, these results suggested that the therapeutic effect of Tongfu decoction on gastrointestinal dysfunction after gastrointestinal surgery was probably exerted via inhibiting the inflammatory storm induced by the PI3K-Akt signaling pathway. e therapeutic mechanism might be the same. e pharmacological effects of the compound may also be applied to other acute abdominal diseases such as severe pancreatitis and acute peritonitis. Also, the indications can be further explored in subsequent studies.
Data Availability e first author should be contacted to request for the data (ravernyflun@outlook.com or +8615202257239).

Conflicts of Interest
e authors declare that they have no conflicts of interest.

Authors' Contributions
Zhenzhou Chen contributed to the conception of the study; Ximeng Zuo, Zhenrui Yang, Xiaojuan Pan, Ze Zhao, and Rui Lai performed the experiment; Xuedan Zhang contributed significantly to analysis and manuscript preparation; Ximeng Zuo performed the data analyses and wrote the manuscript; Xiaoguang Shi helped perform the analysis with constructive discussions.